1. Field of the Invention
The present invention relates to personal-computers generally and more specifically to an apparatus for interfacing a personal-computer to an IBM 3274/6 compatible cluster controller of a 3270 system.
2. Description of the Prior Art
It is common practice to couple a number of terminals to a computer (host) to permit resource sharing. In what is commonly referred to as a 3270-type system, a main frame computer of the type that is commonly designated 370, 30XX or 43XX by the International Business Machines (IBM) Corporation is connected to one, or more, IBM 3274/6-type cluster controllers (control units) each of which is connected to a number of IBM 3278/9-type terminals (display stations). In such a system, controller-terminal communication is over a single-wire coaxial cable by means of a serial by bit, dipulse (biphase) format at a relatively high (2.3587 Megahertz bit) rate. (The protocols for controller-terminal interconnection and communication are discussed in the IBM document entitled "IBM 3274, 3276 Control Unit to Device Product Attachment Information".) Unfortunately, IBM 3278/9-type terminals (and terminals compatible therewith) are relatively expensive.
Personal-computers, such as, for example, those of the IBM-type (IBM PC), are gaining popularity as an alternative to the use of a terminal connected to a system of the above-mentioned type. Although providing considerable computing power, absent a connection to such a system, personal-computers are disadvantageous in that they are unable to provide many of the resources of such a system including the computing power of a main frame computer, the data base of the main frame computer and/or the system and the networking power of the system. (For a technical discussion of the IBM personal-computer the reader is referred to the IBM user manuals generally and particularly to the manual designated "Hardware Design and Interface Information 6025008.")